Gmail is Google's Web-based e-mail service. It was one of the first e-mail services to offer users 1GB of storage space for their e-mails at a time when others were offering just a few megabytes. One of the reasons Gmail has become so popular is its sorting system, which lets users simply leave e-mail in their in-box. Instead of organizing things in folders, Gmail has employed a filtering system, which essentially lets users automatically tag and sort through incoming e-mail.

In 2008 Gmail introduced "labs," a new section of the site where users can test out features that have not yet been released to the main product. It also added Gears, which lets users read, search, and create mail while offline.